An electrostatic chuck has been used to fix a wafer in a semiconductor producing apparatus. The electrostatic chuck includes an internal electrode for applying a voltage and a dielectric layer stuck on the internal electrode and is configured so that, when a voltage is applied to the internal electrode with the wafer disposed on the electrostatic chuck, an electrostatic chucking force is generated between the dielectric layer and the wafer. There are two types of electrostatic chucks, that is, a monopolar electrostatic chuck having one internal electrode and a bipolar electrostatic chuck having a pair of internal electrodes (namely, two) disposed separately from each other. In the monopolar electrostatic chuck, the electrostatic chucking force is generated when a voltage is applied between the internal electrode and an external electrode disposed outside of the electrostatic chuck. In the bipolar electrostatic chuck, the electrostatic chucking force is generated when a voltage is applied between the pair of internal electrodes.
Electrostatic chucks are roughly divided into Johnson-Rahbek electrostatic chucks in which a dielectric having a volume resistivity of about 108 to 1012 Ω·cm is used to generate a Johnson-Rahbek force to attract a wafer, and Coulomb electrostatic chucks in which an insulator (having a volume resistivity exceeding 1016 Ω·cm) is used as a dielectric to generate a Coulomb force to attract a wafer. In a Johnson-Rahbek electrostatic chuck, while a high chucking force is obtained, not only is an expensive power supply having high current capacity necessary but also a slight current flows to a wafer due to a leakage current from the power supply. Accordingly, there is a concern that an integrated circuit formed on the wafer may be electrically damaged. In connection with this, in recent years, Coulomb electrostatic chucks having a lower leakage current are more frequently adopted. However, such a Coulomb electrostatic chuck has a problem in that an electrostatic chucking force is low compared with that of the Johnson-Rahbek electrostatic chuck.
In order to overcome the problem, there have been studies where the volume resistivity of a dielectric was controlled to an appropriate value to increase a chucking force and reduce the leakage current. For example, in Patent Document 1, the volume resistivity is controlled by sintering aluminum oxide with silicon carbide added thereto. Furthermore, in Patent Document 2, the volume resistivity is controlled by sintering aluminum oxide to which magnesium oxide and titanium oxide are added.
[Patent Documents]
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-152065
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2004-22585
However, the silicon compound and the titanium compound used in the Patent Documents 1 and 2 do not have sufficient corrosion resistance to a fluorine-based corrosive gas or plasma thereof, in particular; accordingly, the wafer may be contaminated with conductive particles thereof.